The latest quakes struck Sunday, with the first measuring 6.3 shortly before midday. It triggered landslides and sent people fleeing for cover as parts of Lombok suffered blackouts.
It was followed nearly 12 hours later by a 6.9-magnitude quake and a string of powerful aftershocks.
The picturesque island next to holiday hotspot Bali was already reeling from two deadly quakes on July 29 and August 5 that killed nearly 500 people.
Ten people were killed in the strong quake Sunday evening, mostly by falling debris, including six people on the neighbouring island of Sumbawa, according to the national disaster agency.
Two more Lombok residents died of heart attacks after the morning quake, while some two dozen people were injured and more than 150 homes and places of worship were damaged, the agency said.
Tens of thousands of homes, mosques and businesses across Lombok had already been destroyed by the quake earlier this month.
Most people caught in the latest tremor had been outside their homes or at shelters when it struck which had kept casualties low, said national disaster agency spokesman Sutopo Purwo Nugroho.
“The trauma because of the earlier quake on Sunday (morning) made people prefer to stay outside,” he added.
Aid agencies vowed to boost humanitarian assistance on the island as devastated residents struggled in makeshift displacement camps.
Indonesia’s disaster agency said it was accelerating efforts to rebuild destroyed homes, hospitals and schools, while Save the Children pledged to “scale up” its humanitarian response.
“We are gravely concerned about the repeated distress caused to children by the multiple shocks,” the relief agency said.
‘Too scared at home’
Video images from an evacuation camp in Lombok showed children and adults taking cover inside makeshift tents.
“I’m too scared to stay at my house because it’s damaged,” said resident Saruniwati, who like many Indonesians goes by one name.
“I’ve been here since the quake (earlier this month). I went home two days ago and now I’m back here again.”
Local Agus Salim said the powerful tremor jolted him awake Sunday evening.
“The earthquake was incredibly strong. Everything was shaking,” he told AFP.
“Everyone ran into the street screaming and crying.”
There were landslides in a national park on Mount Rinjani where hundreds of hikers had been briefly trapped after the quake in late July. The park has been closed since then.
Sunday’s tremors were also felt on Bali but there were no reports of damage there.
‘Ring of Fire’
The latest tremor follows the a shallow 6.9-magnitude quake on August 5 that killed at least 481 people and left thousands more injured.
The hardest-hit region was in the north of the island, which has suffered hundreds of aftershocks.
A week before that quake, a tremor surged through the island and killed 17.
The disasters have raised fears that Lombok’s key tourism industry would take a beating, but the international airport was operating normally Monday with no exodus of frightened tourists.
Indonesia sits on the so-called Pacific “Ring of Fire”, where tectonic plates collide and many of the world’s volcanic eruptions and earthquakes occur.
The Australian and Eurasian plates, which sit under the archipelago, have been colliding and putting stress on key area fault lines, according to a geologist.
“Clearly there are different parts of the fault that are moving at the moment releasing those stressors,” said Chris Elders, an expert in plate tectonics and structural geology at Curtin University in West Australia.
In 2004 a tsunami triggered by a magnitude 9.3 undersea earthquake off the coast of Sumatra in western Indonesia killed 220,000 people in countries around the Indian Ocean, including 168,000 in Indonesia.